Frustrated Lewis pairs chemistry

In the field of frustrated Lewis pair chemistry, organoaluminum compounds are often employed as the Lewis acid of the pair to great effect Just as aluminum is a substitute for boron in this case, carbenes are often substituted for the standard phosphines as mentioned in Section 15.5.1. Zhang et al. [137] used several frustrated Lewis pair combinations (A1(C6F5)3 with a variety of phosphines and carbenes) to facilitate the polymerization of methyl methacrylate, a-methylene-y-butyrolactone, and y-methyl-a-methylene-y-butyrolactone. Even combinations that form classical Lewis acid/base adducts rather than FLPs could still exhibit excellent polymerization activity. 

In 2009, Gates and coworkers [255] found that the reaction of IMes with a substituted phosphaalkene resulted in substitution at the C4 position of the carbene, rather than the formation of an adduct through the carbeneic carbon. Later, Bates and Gates invoked the concept of frustrated Lewis pair chemistry to explain this surprising result, suggesting that the formation of an FLP between... 

Stephan, D. W Erker, G. Frustrated Lewis Pair Chemistry of Carbon, Nitrogen and Sulfur Oxides. Chem. Sci. 2014,5, 2625-2641. 

Does the presence of excessive steric bulk when a Lewis acid and a Lewis base attempt to form an adduct automatically render these species inert towards each other The unique behavior of sterically frustrated Lewis pairs (FLPs), pioneered by Stephan, is a vigorous research area with applications for small molecule activation and catalysis." The highly Lewis acidic and sterically bulky tris(pentafluorophenyl)borane" plays a role in many FLP reactions. The great promise of FLP chemistry was revealed by reactions between tris(pentafluorophenyl)borane and tertiary and secondary phosphines, where sterics preclude formation of classic adducts. A seminal example of a frustrated Lewis pair is that of the secondary phosphine di(2,4,6-trimethylphenyl)phosphine that is precluded from forming a classic adduct with tris(pentafluorophenyl)borane. The phosphine Lewis pair is frustrated since it cannot interact with boron to form the adduct. 

Erker G, Stephan DW (2013) Frustrated Lewis pairs I—uncovering and understanding. Topics in current chemistry 332... 

N-HeterocycHc carbenes in the chemistry of frustrated Lewis pairs 13TCC(334)121. 

Group 13 element compounds play a leading role in materials chemistry, i.e., as Ziegler-Natta co-catalysts [42,43] as well as in frustrated Lewis pair (FLP) hydrogen activation and transfer [44 6]. In such reactions it is inevitably important to fine-tune the Lewis acidity of borane compounds. In bis(pentafluorophenyI)(iV-pyrroIyI) borane (1) (Fig. 5, top), only one substituent in the omnipresent B(C6Fs)3 is substituted by a pyrrolyl heterocycle and changes the reactivity only slightly. 

The reaction between a Lewis acid group 13 species of the type R3M and a group 15 Lewis base of the type ER 3 typically yields the corresponding Lewis acid-base adduct R3M-ER 3. This reaction, of fundamental interest in main group chemistry, has recently received an increased attention due to the potential use of amine-borane adducts as a hydrogen storage material [39] and to the unusual reactivity of so-called Frustrated Lewis pairs [40-42]. 

This chemistry resembles that of frustrated Lewis-pairs and it serves for redox-innocent metals as an alternative to oxidative addition reaetions for metals with accessible oxidation states. 

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